Electromagnetically operated D.C. power contactors have been known heretofore. These prior contactors have used various means in an attempt to improve their high fault current withstandability. One such means has been to increase the size of the magnet in an attempt to maintain enough contact pressure during high fault current conditions. However, this means has the disadvantage that the magnet must be prohibitively large. Another means has been to put a holding coil around the current-carrying member to apply additional force to the contacts when needed during the fault current period. However, this means has the disadvantage that additional apparatus must be incorporated into the contactor resulting in increase in both size and cost. It has also been known to use auxiliary contacts and interlocks between the movable contact and the arc shield. However, these two features have often been incorporated in prior contactors in a rather cumbersome and expensive manner without the direct action and simplicity of the present invention. While such prior contactors have been useful for their intended purpose, this invention relates to improvements thereover.